1. Field of the Invention
This invention relates in general to earth boring drill bits, and in particular to the positioning of wear resistant inserts on the cutters.
2. Description of the Prior Art
Earth boring bits for drilling oil and gas wells typically have three rolling cutters that roll over the bottom of the borehole as the bit rotates. Each cutter is generally conical and has a gage surface that contacts the borehole wall as the cutter rotates. One type of bit has wear resistant inserts secured in holes in the cutters. The inserts are arranged in circumferential rows at various distances from the gage surface.
Certain cutters have a gage row structure that includes staggered rows located next to the gage surface. The staggered rows comprise two rows of inserts alternately spaced so that the inserts of one row alternately contact the borehole bottom with the inserts of the other row. Often, the inserts of the staggered rows are spaced as closely as possible to each other to provide as many inserts as is possible for a selected cutter diameter. The minimum distance between inserts is limited by the necessary amount of cutter support metal between inserts.